Another IF pentode which may have some interesting audio applications is the EF184, It has a similar gm and rp as the 6EJ7. so it should be similarly applicable.
http://frank.pocnet.net/sheets/010/e/EF184.pdf
(I just checked through TDSL, EF184 and 6EJ7 are interchangeable)...
I obtained over a dozen of these, NOS/NIB Amperex Bugle Boy EF184s last October at thge NEAR-fest hamfest in Derfield NH. Seller had numerous "flats" (beer cases) filed with tubes, for $15 each, and the se held up to 120+ tubes each. hey were a mix of used, pulls and NOS / NIB,
and he did allow cherry picking so I exchanged the numerous 1B3s, etc ffor more "useful" and intresting tubes. The EF184s werre just a "blind shot" as they 1: looked nice, and 2: had more possible applications than 1B3s and other TV rectifiers...
These have the external "screen" around the anode, and being Amperex BBs made them doubly interesting... Especially when they averaged at under 15 cents each Yellow_Light_Colorz_PDT_06
The "flats" didn't have a lot in the way of truly "desirable" tubes, but then I got these on the second day of the 'fest and I'm sure that all of the good ones were already well picked over... I was there both days, but not over Friday night, and that is when some of the best deals seem to surface...
It was too darn cold and I didn't want to freeze my butt off while "car camping".
/ed B